The coal mixture screened through a $20-$mesh screen and the screen analysis data is shown below. Calculate the ratio of overflow to feed and underflow to feed, and overall screen effectiveness $($E$)?($Answer: D$/$F $=0\mathrm{.}68461$; B$/$F $=0\mathrm{.}31538$; E$=69\mathrm{.}91\%)$Mesh No$.$Screen opening, Dpi $($cm$)$Weight retained $($in terms of $\%)$ FeedOverflowUnderflow$40\mathrm{.}469914\mathrm{.}320\mathrm{.}080\mathrm{.}236220\mathrm{.}028\mathrm{.}0140\mathrm{.}116820\mathrm{.}028\mathrm{.}010\mathrm{.}5280\mathrm{.}058928\mathrm{.}524\mathrm{.}029\mathrm{.}5480\mathrm{.}02958\mathrm{.}630\mathrm{.}01000\mathrm{.}01475\mathrm{.}720\mathrm{.}01500\mathrm{.}01042\mathrm{.}910\mathrm{.}0$